Rare-earth permanent magnet and method for manufacturing rare-earth permanent magnet

Abstract

There are provided a rare-earth permanent magnet and a manufacturing method thereof capable of simplifying manufacturing process and improving productivity through advanced ability to produce net shapes. In the method, magnet material is milled into magnet powder, and the magnet powder and a binder are mixed to prepare a mixture. Next, the prepared mixture is formed into a green sheet. Thereafter, the green sheet is held for predetermined time at binder decomposition temperature in non-oxidizing atmosphere, whereby depolymerization reaction or the like changes the binder into monomer and thus removes the binder. The green sheet with the binder removed therefrom undergoes pressure sintering such as SPS method so as to obtain a rare-earth permanent magnet 1.

1 . A rare-earth permanent magnet manufactured through steps of:
 milling magnet material into magnet powder;   preparing a mixture of the magnet powder and a binder;   obtaining a green sheet by forming the mixture into a sheet like shape; and   pressure sintering the green sheet.   
     
     
         2 . The rare-earth permanent magnet according to  claim 1 , wherein, in the step of pressure sintering the green sheet, the green sheet is sintered by uniaxial pressure sintering. 
     
     
         3 . The rare-earth permanent magnet according to  claim 1 , wherein, in the step of pressure sintering the green sheet, the green sheet is sintered by electric current sintering. 
     
     
         4 . The rare-earth permanent magnet according to  claim 1 , wherein, before the step of pressure sintering the green sheet, the binder is decomposed and removed from the green sheet by holding the green sheet for a predetermined length of time at binder decomposition temperature in a non-oxidizing atmosphere. 
     
     
         5 . The rare-earth permanent magnet according to  claim 4 , wherein, when decomposing and removing the binder from the green sheet, the green sheet is held for the predetermined length of time at temperature range of 200 degrees Celsius to 900 degrees Celsius in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and inert gas. 
     
     
         6 . A manufacturing method of a rare-earth permanent magnet comprising steps of:
 milling magnet material into magnet powder;   preparing a mixture of the magnet powder and a binder;   obtaining a green sheet by forming the mixture into a sheet like shape; and   pressure sintering the green sheet.   
     
     
         7 . The manufacturing method of a rare-earth permanent magnet according to  claim 6 , wherein, in the step of pressure sintering the green sheet, the green sheet is sintered by uniaxial pressure sintering. 
     
     
         8 . The manufacturing method of a rare-earth permanent magnet according to  claim 6 , wherein, in the step of pressure sintering the green sheet, the green sheet is sintered by electric current sintering. 
     
     
         9 . The manufacturing method of a rare-earth permanent magnet according to  claim 6 , wherein, before the step of pressure sintering the green sheet, the binder is decomposed and removed from the green sheet by holding the green sheet for a predetermined length of time at binder decomposition temperature in a non-oxidizing atmosphere. 
     
     
         10 . The manufacturing method of a rare-earth permanent magnet according to  claim 9 , wherein, when decomposing and removing the binder from the green sheet, the green sheet is held for the predetermined length of time at temperature range of 200 degrees Celsius to 900 degrees Celsius in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen and inert gas.